Manufacture of artificial filaments, threads, and films



Patented Aug. 28, 1923.

U TI. TS

CHARLES WILFRED JPALMER AND wILLmM'nLnxANnEn mourn, or sr'onnoiv, w enDERBY, ENGLAND, sssrenon-s T0 111mm; narrrrus, or Lonnois, ENGLAND.

MANUFACTURE OF AR'JJIZEICIAL FILAMENTS, THREADS, AND FILMS.

No Drawing.

To all whomz't may concern: 7

Be it known that we, CHARLEs WILFRED PALMER and WIILIAM ALEXANDERDIOKIE, subjects of-the King of Great Britain, both of Spondon, nearDerby, England, have 1nvented certain new and useful ImprovementsvRelating to the Manufacture of Artificial Filaments, Threads, and Films,of which the following is a specification.

It has been proposed to manufacture artificial filaments and films fromsolutions-of cellulose acetate in organic solvents that are soluble inor miscible with water, by squirting or extruding the cellulose acetatesolutions into aqueous coagulating baths.

Hitherto it has not been possible to obtain strong and elastic filamentsor films by such methods, owing to the fact that the cellulose acetateis not coagulated by water in the form of a structurally continuous gel,but with a discontinuous granular or reticulated internal structure, sothat the resulting threads or films are lacking in strength andelasticity.

We have found that ammonium thiocyanate and other thiocyanates, such forexample as those of sodium, potassium and calcium, are capable, owing toa latent solvent power which they have for cellulose acetate, ofexerting a swelling and coagu lation controlling action on thecoagulating filaments or films and thereby tending to preservecontinuity of structure and to prevent the too complete shrinkage of thecellulose acetate which ordinarily occurs as the result of the removalof the organic solvent by the aqueous coagulating bath and causesprecipitation of the cellulose acetate with a discontinuous structure.

Accordin to the present invention, in order to o viate the diflicultybefore referred to, we add ammonium thiocyanate or other thiocyanates tothe coagulating baths, or we may incorporate the same with the celluloseacetate solutions to be spun or formed into filament or films.

By means of the invention we have found that it is possible to obtainstrong, elastic, translucent and lustrous filaments or films.

The invention applies in particular to the manufacture of artificialfilaments or films from acetone-soluble cellulose acetates, but

may also be employed with other acetates of cellulose.

In practising the invention the thiocya- Application filed December 20,1921. Serial No. 523,758.

nates should not be employed in too-great quantity or concentration, asotherwise they could exert too great a solvent power and preventcoagulation of the cellulose acetate. On the other hand they; should bein sulficient quantity or concentration to exert the required modifyinginfluence on the shrinking action of the water.

In carrying out the invention, solutions of cellulose acetate in anyorganic solvents miscible with water (both hereinafter in the claimingclauses included in the term miscible with water) or soluble in watermay be employed, for example acetone, or acetone-alcohol mixtures, withor without suitable plastifying agents, as for instance benzyl alcohol.v

The manner in which the invention may be carried into effect isillustrated by the" carried forward inthe thread is removed by washing,and the purified translucent threads of cellulose acetate are dried. Thefilaments issuing from the squirting nozzle are endowed withconsiderable strength, and

the combined action of the water and the thiocyanate swelling agent aresuch that the cellulose acetate solutiorymay be drawn out to filamentsof great tenuity from orifices of relatively large diameter. In this wayit is easily possible to obtain artificial silk filaments of very lowdenier, for example as fine as 1 or 2 or less denier, that is to say asfine as natural silk.

It is understood that the limits of concentration of the thiocyanatesalt may be varied to suit desired conditions.

Mixtures of the thiocyanates may likewise be employed as beforementioned, in'the coagulating bath. For instance, mixtures of any two ormore of. the thiocyanates of ammonium, sodium, potassium and calcium maybe employed in about the same total promrtions as above mentioned, sayabout 115 to 120 grams total thiocyanate per litre of water, but thelimits of concentration may be varied as above mentioned. If aplasticising agent is employed, the solution .might contain 16 parts ofcellulose acetate dissolved in 80 parts of acetone containing,

about i parts of benzyl alcohol as plasticisin agent.

Vhat We claim and desire to secure by Letters Patent is 1. In a processfor the manufacture of filaments, threads or films, extruding celluloseacetate in solution into an aqueous coagulating bath containingthiocyanate in solution.

2. In a proces for the manufacture of filaments, threads or films,extruding a solution comprising cellulose acetate and an organic solventthereof miscible with water,

into an aqueous coagulating bath containsubscribed our names. I

CHARLES WKLIFLIED PALMER.

WILLIAM ALEXANDER DICLSLIE. Witnesses:

' Time. II. Coox,

A. A. GUNNING.

